Fireproof fuel tank system



May 15, 1945. B. WALKER 2,375,834

FIREPROOF FUEL TANK SYSTEM Filed March 1o, 194s Patented May l5, i945 STATES PATENT OFFICE (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 O. G. 757) 3 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without, the payment to me of any royalty thereon.

This invention relates to a system for making the fuel tank of a self-propelled vehicle substantially lireproof. The invention relates particularly to combat aircraft, although it is of course not so limited in its use.

A perpetual nightmare for a Apursuit pilot or the crew of a bomber is the possibilities for fire which are inherent wherever `gasoline is present, especially the highly volatile gasolines used in planes. It has Ibeen found that the air-vapor mixture above the liquid in the tank is likely to be explosive when the tank is from to 50% full, and at 10 F. or colder. These are, of course, precisely the conditions likely to be encountered in combat. It may be noted that these specifications may vary with the kind of gasoline. In general, however, explosive mixtures form when the tank is about half or less than half full, and when the temperature is low enough to reduce the vapor pressure of the gasoline to the point where the vapor space is not filled completely with gasoline vapor.

It is the object of this invention to provide a fuel system in which the danger of nre from bullets, including tracers and incendiaries, piercing the tank is substantially reduced. This object is accomplished by keeping the vapor space above the liquid lled with an inert gas. This gas is supplied from the exhaust of the internal combustion engine or other power plant which drives the vehicle or vehicle auxiliaries. Means are provided to cool the gas and to insure that sparks and moisture will not pass to the vapor space.

Figure 1 of the drawing shows a preferredem- 4 bodiment of the invention, in which a watercooled internal combustion engine provides the exhaust gas for the fuel tank vapor space.

Figure 2 is a fragmentary view of a modified form of my invention. Referring to the drawing in detail, a fuel tank is shown at 2, having a quantity of fuel 4 in it. The space 6 above the tank is adapted to be filled by an inert gas, which is preferably provided by by-passing some of the exhaust gas`.z-,-from the power plant 8 of the vehicle. Powerf-plant 8 is provided with an exhaust gas outlet conduit I0. A by-pass connection l2 takes some gas from conduit I0 to flll the vapor space B. 'I'he gasentrance end of connection I2 is preferably CSI passed exhaust gas the benefit of the kinetic energy of the gas in conduit I0.

Any suitable llame or fire screen, or spark arrester, will preferably be provided at I6. To condense a major portion of the water vapor out of the gas, a cooler I8 is provided. A trap 20 in the lower part of the cooling coil is provided with a drip 22 to permit the discharge of condensed moisture. Such water vapor as is not thus removed is taken out in a suitable dehydrator 24.

If necessary, a pump 26, such as a centrifugal pump, may be provided in connection I2 to boost the pressure of the gas ygoing to the tank. A hand valve 28 may conveniently be provided to permit.

isolation of the tank from the exhaust gas conduit.

In order to permit a continuous ilow of exhaust gas through the vapor space 6 and to prevent building up too great a pressure in the tank when the plane climbs rapidly, a low positive pressure relief valve 30 is preferably provided in the upper wall 32 of the tank. It Will be understood that a conduit, not shown, may be provided to carry the discharged exhaust gases away from the tank, rather than simply dump those gases out through valve 30. A check valve 33 is provided to prevent gasoline fumes owing back into the dehydrator, cooler and exhaust line.

'I'he tank 2 is provided with the conventional capped. fuel inlet 34. Suitable bailes as shown at 3'6 may be provided to keep fuel from sloshing out through valve 30.

In operation, particularly in pursuit planes, ascent and descent are likely to be very fast at times, resulting in some rather rapid atmospheric pressure changes. In a power dive, the pressure outside tank 2 will rise rapidly, necessitating a fast build-up of internal pressure by the exhaust j gas to prevent collapsing the tank. The connection l2 should therefore have sufllcient carrying capacity to be able to supply exhaust gas tothe tank as fast as it is required to maintain the desired pressure differential.

It can thus be seen that the usual explosive mixture above the liquid in the tank is supplanted by an inert gas, thus substantially reducing the fire hazard in case bullets should pierce the tank.

Under some circumstances, it may be desirable to have a pressure less than atmospheric in the vapor space above the tank. This negative pressure should be enough to overcome the static head of fuel, as explained in detail in my previous case, Serial No. 439,533, filed April 18, 1942. In the event that a vacuumor a pressure less than pointed upstream as shown at I4 to give the by- 55 atmospheric pressure is desired in the tank, an

arrangement as showniri Figure 2 provided wherein a suction pump ill-iis,V disposed "inl the connection l2 in adirectionreversed-to that of the pump 26 shownvin Figure 1.".'Itfwil1 be evident that as the fuel in the vtank i's consumed,'

and the fuel tank, it will be evident that a partial vacuum can be maintained. A partial vacuum in the fuel tank reduces' the shocking effect of the fuel tank materially when it is penetrated lby high velocity bullets or fragments. The partial vacuum also reduces the tendency of the fuel to leak out of the tank. Exhaust gas will flow against the pump into the vapor space, the pump serving merely to maintain a predetermined differential between the atmospheric pressure and the pressure in the tank. A

It will be evident from the foregoing that I have provided a novel combination of devices between the exhaust line of an internal combustion engine and a fuel tank for high volatile fuel wherein the hot inert gases from the exhaust line are cooled, dehydrated, and run through a pump or a pressure control valve (not shown) into the Variousl changesmay be made the'vspeciiic v embodiment-of my invention-without departing from v the spirit thereof, or from the scope of the appended claims. u

I claim: A

1. In combination with a storagetank for high volatileA fuels and the exhaust line of an internal combustion engine, ay iiuid connection therebe- -tween havingin seriatim from said exhaust line to said storage tank, a cooler, a dehydrator. a pump, and a check valve, said check valve permitting inow vof inert exhaust gases into said storagetank vbut preventing outflow of iiuid from said 'storage tank. Y Y

' 2. A system as set forth in claim 1 wherein said connection has a spark arresterdisposed therein immediately adjacent said exhaust line.

3. In combination with a storage tank for high volatile-fuel and the exhaust line of an internal combustion engine, a fluid connection therebetween having in serlatimfrom said exhaust line to said storage tank, a coolerl a dehydrator, a suction pump, a hand valve, and a check'valve, said suction pump tending to maintain the pressure in said storage tank below atmospheric pres- Sure.

BROOKS WALKER. 

